Process for making autotype printing-blocks.



E. ALBERT.

PROCESS FOR MAKING AUTOTYPE PRINTING BLOCKS.

APPLICATION FILED JULY 23, 1908.

Patented June 29, 1909.

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UNITED STATES PATENT oFFro'E.

EUGEN ALBERT, OF MUNICH, GERMANY,

PROCESS FOR MAKING AUTOTYPE PRINTING-BLOCKS.

To all whom it mag concern: Be it known that I, EUGEN ALBERT, a subject of the Emperor of German residin at Munich, in the Kingdom of avaria, orman have invented certain new and useful Ii nprovements in Processes for Making Autotype-Printing-Blocks, of which the following 1s a specification.

This invention relates to an improved process for making auto type printing blocks and has for its object to im rove the dot formation thereon so as to ma e the tones of the picture printed therefrom more perfectly like those of the original picture than have is well known that such blocks-usually called half tone blocks-are printed through a finely divided lass screen and in order to obtain the breaking up of the light values of the half tone negative into oints and lines of suitable dimensions it as hitherto been proposed that during, prior to, or after the copying of the negative, the screen should not ear directly upon the sensitive layer, but be placed at a-slight distance away and the an le of incidence of the light changed. It s ould be noted in this connection that the rays of li ht'are always regarded as parallel in themse%ves owing to the minuteness of the screen aperture and to the slight distance of these from the sensitive layer in pro ortion to the great distance of the source of i ht.

Usually the process mentione when using a cross screen was carried out by altering the angle at which the plane of the screen and the sensitive late stood with reference to the source of light; the axis of the annular oscillation had either to form an angle with the line systems of the screen, or else be parallel to one of the systems; in neither case was the point form satisfactor in fact a correct point form with concentrically increasing light intensities, and which is also capable of properly reproducing the light va ues of a negative, or positive, cannot be obtained at all with cross screens by alterations of the angle merely, at which they stand with reference to the source of light.

This invention consists in arranging that the projection of the transparencies of the cross screen upon the sensitive coating is effected at angles lying in. several planes with regard to the source of light amin making the an les of coincidence of the rays of light as small as possible, I having discovered that the smaller the angles and the more planes Specification of Letters Patent. Application filed. July 23, 1908.

- by increasing the Patented June '29, 1909. Serial No. 444,935.

there are the softer is the decline of the curve of intensity of the dot, and as a result the richer are the tones of the reproduction. The reduction of the angles at which the rays of light fall on the sensitive surface is achieved in such a way that the action of the perpendicular rays of light, and of those nearly perpendicular, is materially diminished.

In practice very good results have been given by arrangement such that the central point of the projection described an annular pat the maximum diameter of which is preferably not larger than one side of the projected screen transparency and, if the annular path forms a circle, then allowance must be made for one and the same equal degree of the angleof incidence of the rays of light at each point of the path and in an infinite number of planes. Apparatus for carrying this process into effect is tully disclosed in my 00- ending application, Ser. No. 444,934, filed uly 23/08.

Figures 13 of the accompanying drawings will serve to explain the process diagrammatically.

In Fig. 1 the square shows the projection of a screen aperture, greatly magnified and the circle the ring in which the central point of the projection is to move. In order to give a birds eye view of the matter only 12 points 1-12 are given in the ring, and by the successive displacement of the central point of the square there is produced in lace of these 12 points the figure 2, inwhich tl ie copying intensities are given by means of From these figures there is obtained the form of the doc e of the intensity curve, the field marked 12 is of the greatest intensity, the diminution being radially outward through fields 11 to 1 inclusive. As regards the shape of the dot it is clear that the corners on the outer sides will disappear number of the oints of displacement; by continued operation there is obtained the form-shown by dotted lines in Fig. 3, at four adjacent screen points 12 denoting the centers of the points. If the annular path is exactly a circle then round shaped screen points are formed, but if on the contrary it is somewhat len hened, then the so-called egg shape, or ova bar shape is obtained.

The means employed in practice for causing the screen point projection to follow the required annular path are numerous; this result may be attained by moving the source of li ht in an annular path in a plane parallel to t e plane of the screen, or preferably by moving the copying frame itself in such an annular ath.

What claim as my invention and desire to secure by Letters Patent is 1. The process of making auto type printing blocks from half tone negatives or positives by means of cross screens, which consists in effecting the projection of the transparent spaces of the cross screen upon the sensitive layer of the block, during the copying process in a multiplicity of diflerent non parallel planes with reference to the source of light, the projection of each space thereby progressin along a continuous path, such pro ection eing effected with total or nearly total extinction of the action of the rays of light falling on the surface in angles which are perpendicular, or nearly perpendicular,

thereto.

2. The process of making-auto type printing blocks from half tone negatives or positives by means of cross screens, which consists in effecting the projection of the transparent spaces of the cross screen upon the sensitive layer of the block during the copying process in a multiplicity of different nonparallel planes with reference to the source of light, the projection of each space thereby pro ressing along a continuous path within the limits of such space, such projection being obtained by rays of light falling on the screen at very small angles of incidence, and with total or nearly total extinction of the action of the rays of light falling on the surface in angles which are perpendicular, or nearly erpendicular, thereto.

3. T e process of making auto type printing blocks from half tone negatives or positives by'means of cross screens, which consists in effecting the projection of the transparent spaces of the cross screen upon the sensitive layer of the block during the copying process by altering in different directions the relative positions of the screen, the sensitive surface and the source of light so that the central points of the projections of the'transparent spaces of the screen form a closed annular shaped path, the maximum diameter of which is not substantially larger than one side of the projected transparent space.

4. The process of making auto type printing blocks from half tone negatives or positives by means of cross screens, which consists in effecting the projections of the transparent spaces of the cross screen upon the sensitive layer of the block during the copying process by causin the screen and the sensitive surface to follow an annular path with reference to a fixed source of light such that the central point of the projection of each transparent space of the screen upon said sensitive layer forms a closed annular shaped path the maximum diameter of which is not substantially larger than one side of the projected transparent space.

5. The process of making autotype printing blocks, from half tone negatives or positives by means of cross-screens, consisting in rojecting, during the act of copying, the ight transmitted through each transparent space of the cross-screen upon the sensitive layer of the-block in a multiplicity of successive positions in a curvilinear path and within an area not greater in extent than that of such trans arent space.

In testimony w ereof I affix mysignature 2 in presence of two witnesses.

EUGEN ALBERT.

Witnesses:

LOUIS F. MUELLER, ALMA MAAS. 

